In a thread brake, the thread passing through the brake is mechanically decelerated by means of squeezing and/or deflection. The thread brake constitutes a weak point in the thread path when threading is carried out for the first time or when it is carried out after thread breakage because the thread has to be threaded by hand in some cases through a plurality of thread brakes, and this is time-consuming and complicated. The advantages with regard to ease of handling and stop periods gained by an automatic threading device provided for other components along the thread path are substantially impaired by the manual threading operation in the thread brakes.
This applies to the lamella brakes according to U.S. Pat. No. 4,641,688 or DE-A-21 31 302, in the case of which two lamellae are resiliently pressed against each other or in the case of which one lamella is pressed against a fixed stop means, as well as to the known socalled deflection brakes in the case of which thread guide elements are manually aligned with respect to each other by folding two holding arms towards one another before the thread is threaded by hand.
In the case of a controlled thread brake known from CH-A-310 476, a brake element is pressed against a counter brake element consisting of a tensioned braking strip. The brake element is connected to a cam drive means and it is even adapted to be completely lifted off the counter brake element.
WO 90/11397 describes that cam-controlled thread tensioners and thread brakes with cam-controlled braking fingers are displaced to a threading position for the purpose of threading the thread. However, this arrangement does not comprise any air guide surfaces.